The heavy turbulence that rattled a United Airlines plane headed for Los Angeles and injured 30 people Tuesday evening has drawn attention to turbulence – and what can be done to avoid it.
"We were steering away from some thunderstorms and we hit a severe pocket of turbulence," Sean Gradney, who was on Flight 967, told the Denver Post. "Some people were ejected from their seats. They hit the overhead compartments and they were injured."
Turbulence is a state of air flow in which air speeds irregularly and randomly fluctuate, according to the National Weather Service. It is by nature hard to predict and, therefore, avoid.
However, scientists have uncovered some factors that influence turbulence, and keeping these in mind, people may be able schedule flights accordingly and minimize their chances of being tossed around.
1. Seasons and geography
"How safe an area is to fly over depends on the time of year and the type of turbulence," said Larry Cornman, a physicist at the National Center for Atmospheric Research.
This is in part because the weather conditions that are a major part of turbulence vary from region to region.
During the summertime, areas such as Florida and Kansas often get hit with thunderstorms, which are notorious for causing turbulence. In comparison, Minnesota has fewer thunderstorms during the spring and fall seasons, so flights over it are less likely to be turbulent, Cornman said.
Turbulence can become an issue for people planning to fly over Canada in the summertime, as jet stream air currents are strong there during that time of year, and cause a great deal of clear air turbulence. Jet stream currents move into the United States during wintertime, according to Cornman.
And the landforms below can influence turbulence high in the sky.
"Mountain turbulence is a year-round issue," Cornman said. "People flying near the Cascade Mountains, for example, are likely to experience it."
And while some causes of turbulence are invisible, clouds should be avoided to ensure a smooth flight, Cornmann said.
2. The moon
For night flights, the phase of the moon can influence how well a pilot is able to avoid turbulence. If the moon is full, it acts as a light source for pilots and allows them to see clouds and possible storms that they may not see in darker conditions, Cornman said.
How high an aircraft flies plays a role in the amount of turbulence that is encountered, according to Donald McCann of McCann Aviation Weather Research, Inc., an aviation weather research company in Overland Park, Kan.
"Lower elevations, at 3,000 feet and below, have higher turbulence than higher elevations," said McCann, who has previously worked at the National Weather Service (NWS) and has over 30 years of aviation weather forecasting experience. Airplanes flying near the ground commonly experience "mechanical" turbulence, as winds blowing over and around buildings create eddies, according to the NWS.
However, different forms of turbulence occur at various elevations, and therefore higher elevations are not altogether safer from turbulence than lower elevations, Cornman said. Most commercial planes fly at altitudes of 30,000 to 40,000 feet (9,100 to 12,200 meters), where air density is lower but thunderstorm clouds can still hit, and are sometimes hard to detect.
"For example, convective turbulence occurs when air that is rapidly rising above a thunderstorm reaches an altitude at which an airplane is flying," Cornman said.
What you can do
Wearing seatbelts likely kept many of the 265 people on flight 967 from being injured. It is important to keep seatbelts on for as much of the flight as possible, even if the seatbelt sign has been turned off, experts say.
This is because one form of turbulence, called clear air turbulence, can strike literally out of the blue, Federal Aviation Administration (FAA) spokesman Les Dorr told LifesLittleMysteries. Clear air turbulence is impossible to detect or predict unless an airplane flying ahead experiences it and warns the planes behind it, Dorr said.
"It's the flight attendants who sustain the most injuries during turbulence, and that's simply because they are, by virtue of their jobs, out of their seats more than anyone else on the airplane," wrote Captain Meryl Getline, a retired captain from United Airlines in her USA Today column in 2005.
In fact, four of the 10 crew members on flight 967 were injured, compared to 26 out of 255 passengers.
"Buckling up makes all the difference in the world, so please keep this in mind next time you fly," Getline advised.LifesLittleMysteries, a sister site to LiveScience.